Wiper device for stripping drilling fluid from rig drill string

Abstract

The wiper device comprises an elongated conveyor arm which can pivot in a horizontal plane and freely move forward and backward through a limited travel (which movement capabilities are collectively termed "floating" capability). The arm carries a wiper pad assembly on its outer end. The wiper pad assembly can therefore float with the arm to accommodate lateral and to and fro sway of the drill string within the confines of the rig rotary table bushing, when the wiper pads are engaged with the drill string. The arm can be advanced and withdrawn to convey the wiper pad assembly between the operative stripping position over the bushing and a retracted position off to one side of the bushing.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as: follows: 
     
       1. A wiper device for stripping drilling fluid from a drill string being pulled through the rotary table bushing of a drilling rig comprising: a support member having a horizontally extending support surface means;   a conveyor arm supported by the support surface means and coupled to the support member, said conveyor arm being operative to slide along the support surface means to move between stripping and retracted positions;   first biasing means for advancing and retracting the conveyor arm between the positions, the means being connected at its outer end to the conveyor arm;   a wiper pad assembly having side opening and closing wiper pads for stripping drilling fluid from the drill string, said wiper pads being pivotally mounted on the conveyor arm for pivoting between a closed stripping position and an open disengaged position said assembly being carried by the outer end of the conveyor arm;   the wiper pad assembly, first biasing means and conveyor arm forming a first unit;   connector means slidably connecting the inner end of the first biasing means with the support member so that, when the first biasing means is extended to center the wiper pads over the bushing, the sliding connector enables the first unit to move either forwards or backwards with the drill string until it contacts the bushing;   whereby the first unit may float with the drill string when the latter is swaying as it is being pulled through the bushing.   
     
     
       2. The wiper device as set forth in claim 1 wherein: the support member is rotatable about a substantially vertical axis and the conveyor arm is coupled thereto so as to rotate therewith;   the support member forms a slide path having a rear stop, and   the connector means comprises   a plate, retained by the support member and positioned to slide back and forth along the slide path, the rearward travel of the plate being limited by the stop, and   elastic resilient means for normally urging the plate and first unit forwardly.   
     
     
       3. The wiper device as set forth in claim 2, wherein the wiper pad assembly comprises: a pair of overlapping wiper pad carriers carrying the wiper pads and being operative to pivot together or apart in a substantially horizontal plane about a common pivot point,   a second cylinder means carried by the conveyor arm,   linkage means connecting the second cylinder means with the wiper pad carriers, said linkage means being operative to open and close the carriers equally in response to the second cylinder means contracting and expanding; and   an accumulator tank connected with the second cylinder means for allowing a drilling string enlargement to spread apart the wiper pads without significantly changing the fluid closing pressure.   
     
     
       4. The wiper device as set forth in claim 1 wherein: the support member forms a generally horizontal, elongated support surface and   the conveyor arm is an elongated beam positioned on the support surface.   
     
     
       5. The wiper device as set forth in claim 4 wherein: the first biasing means is a double acting cylinder having one end connected to the conveyor arm and its other end connected to the connector means.   
     
     
       6. The wiper device as set forth in claim 5, wherein the wiper pad assembly comprises: a pair of overlapping wiper pad carriers carrying wiper pads and being operative to pivot together or apart in a substantially horizontal plane about a common pivot point.   a second cylinder means carried by the conveyor arm,   linkage means connecting the second cylinder means with the wiper pad carriers, said linkage means being operative to open and close the carriers equally in response to the second cylinder means contracting and expanding; and   an accumulator tank connected with the second cylinder means for allowing a drilling string enlargement to spread apart the wiper pads without significantly changing the fluid closing pressure.   
     
     
       7. The wiper device as set forth in claim 1, wherein the wiper pad assembly comprises: a pair of overlapping wiper pad carriers carrying the wiper pads and being operative to pivot together or apart in a substantially horizontal plane about a common pivot point,   a second cylinder means carried by the conveyor arm,   linkage means connecting the second cylinder means with the wiper pad carriers, said linkage means being operative to open and close the carriers equally in response to the second cylinder means contracting and expanding; and   an accumulator tank connected with the second cylinder means for allowing a drilling string enlargement to spread apart the wiper pads without significantly changing the fluid closing pressure.   
     
     
       8. A wiper device for stripping drilling fluid from a drill string being pulled through the rotary table bushing of a drilling rig, comprising: a wiper pad assembly comprising a pair of side opening and closing wiper pads for stripping drilling fluid from the drill string;   means for carrying the wiper pad assembly between a retracted position spaced from the drill string and a stripping position where the wiper pads can close around the drill string;   means for biasing the carrying means between retracted and stripping positions;   the wiper pads being pivotally mounted on the carrying means for pivoting in a horizontal plane between a closed stripping position and an open disengaged position;   means for actuating the wiper pads to open and close them;   the carrying means being operative to pivot in a horizontal plane and to reciprocate to and fro, so that the wiper pads may float with the drill string when closed therearound in the stripping position, as the drill string sways within the limiting confines of the table bushing.   
     
     
       9. The wiper device as set forth in claim 8 wherein the wiper pad assembly comprises: a pair of overlapping wiper pad carriers carrying the wiper pads and being operative to pivot together or apart in a substantially horizontal plane about a common pivot point,   a second cylinder means carried by a conveyor arm,   linkage means connecting the second cylinder means with the wiper pad carriers, said linkage means being operative to open and close the carriers equally in response to the second cylinder means contracting and expanding; and   an accumulator tank connected with the second cylinder means for allowing a drilling string enlargement to spread apart the wiper pads without significantly changing the fluid closing pressure.   
     
     
       10. The wiper device as set forth in claim 8 wherein: the carrying means is a longitudinally movable conveyor arm; and   the wiper pads are pivotally mounted on the conveyor arm for pivoting about a common pivot point between the disengaged and stripping positions.   
     
     
       11. The wiper device as set forth in claim 10, wherein the wiper pad assembly comprises: a pair of overlapping wiper pad carriers carrying the wiper pads and being operative to pivot together or apart in a substantially horizontal plane about a common pivot point,   a second cylinder means carried by the conveyor arm,   linkage means connecting the second cylinder means with the wiper pad carriers, said linkage means being operative to open and close the carriers equally in response to the second cylinder means contracting and expanding; and   an accumulator tank connected with the second cylinder means for allowing a drilling string enlargement to spread apart the wiper pads without significantly changing the fluid closing pressure.   
     
     
       12. The wiper device as set forth in claim 10 comprising: a support member supporting the conveyor arm, the conveyor arm being longitudinally slidable to and fro on the support member;   a cylinder for biasing the conveyor arm to and fro, the cylinder being connected between the conveyor arm and the support member, the cylinder having a sliding connection with the support member; and   spring means normally urging the conveyor arm to the extended position;   so that the sliding connection enables the conveyor arm to move either forward or backward with the drill string until the drill string contacts the bushing.   
     
     
       13. The wiper device as set forth in claim 12, wherein the wiper pad assembly comprises: a pair of overlapping wiper pad carriers carrying the wiper pads and being operative to pivot together or apart in a substantially horizontal plane about a common pivot point,   a second cylinder means carried by the conveyor arm,   linkage means connecting the second cylinder means with the wiper pad carriers, said linkage means being operative to open and close the carriers equally in response to the second cylinder means contracting and expanding; and   an accumulator tank connected with the second cylinder means for allowing a drilling string enlargement to spread apart the wiper pads without significantly changing the fluid closing pressure.